DESCRIPTION (Investigator's Abstract): The broad aim is to develop a diagnostic approach for Creutzfeldt-Jakob disease (GJD), based on characterization of disease-associated cerebrospinal fluid (CSfl proteins. This will be achieved by direct comparison to reference maps of normal cSF proteins, and will also include a measure of each patient's specific pathology. The underlying hypothesis is that a) there is a unique distribution of proteins for each body fluid, cell type and tissue that can, like a fingerprint, provide a reference map that is specific for each fluid, cell type or tissue; b) damage to the nervous system will lead to addition of disease-associated proteins that are distinct from the normal CSF proteins; c) those diagnostic proteins not found in normal CSF will reveal the source(s) when they are found in the reference maps of other cells, tissues or body fluids; d) the identified source of disease-associated proteins will provide interpretation of the cellular and molecular pathology in each patient. Specifically, common reference maps will be made from normal "volunteers" for CSF plasma, red and white blood cells and brain tissue. Such maps will be compared from the 1000-5000 protein spots of high resolution two dimensional electrophoretic gel patterns of each sample. Experiments on multiple gels of the same sample and separate cohorts for each sample group will define the technical and biological variations. Extra proteins in the CSF from patients with will then be identified by comparison with the normal CSF map. These additional associated CSF proteins will be compared to the other fluid, cell and brain tissue maps to identify their protein source. Proteins that distinguish the patients with will be further characterized by partial amino acid sequence analysis and peptide mapping, both to establish their molecular identity and to enable more detailed investigation of individual proteins. The results of this study should indicate the utility of this approach for other human disease.